“#Al-Nusra Front: a cafe belonging to the (Alawite Arab) Democratic Party in Jabal Mohsen was targeted with a double martyrdom attack, to avenge the Sunnis in Syria and Lebanon,” read the tweet.

The Arab Democratic Party is the main group representing the Alawite minority in Lebanon.

Syria conflict fuelling sectarian hatred –

Lebanese politicians and movements were quick to condemn the bombing, branding it a “terrorist” act and calling for unity.

“This crime will not terrorise the Lebanese or the residents of Tripoli, and it will not weaken the government’s resolve to confront terrorism and terrorists,” Prime Minister Tammam Salam said in a statement.

The powerful pro-Syrian Shiite Hezbollah movement blamed “takfiri (extremist) terrorists” for carrying out the attack, in a reference to radical Sunni militants.

Former prime minister Saad Hariri, Lebanon’s main Sunni official, also condemned the attack.

“This terrorist act is part of a campaign to sow chaos and division, and to destabilise (Tripoli) after the Lebanese army and security forces managed to stop the cycles of violence,” Hariri said in a statement.

Lebanon’s second city Tripoli has seen frequent violence pitting gunmen in the Alawite district of Jabal Mohsen against neighbouring Sunni Bab al-Tebbaneh.

Fighting between the two districts in recent years has killed scores of people, many of them civilians caught in the crossfire.

Though the tensions have their roots in the 1975-1990 Lebanese civil war, sectarian hatred has spiralled ever since the outbreak of a revolt in neighbouring Syria.

Residents of Jabal Mohsen support Syria’s President Bashar al-Assad, who belongs to an Alawite clan, an offshoot of Shiite Islam, that has ruled the war-torn country for more than 40 years.

People in Bab al-Tebbaneh support the rebels, who like the Syrian population are mostly Sunni.

Since October, the army has deployed heavily in Tripoli, detaining hundreds of people in an attempt to stem the violence.

On August 23, 2013, bomb attacks struck two mosques in Tripoli, killing and wounding dozens of people.

Some of those suspected of involvement in the attacks were from Jabal Mohsen. (AFP)